Compared to conventional illumination light source, LEDs are small, have high efficiency and long product life. LEDs are considered as a new illumination light source for conventional lamps such as fluorescent light and incandescent light bulb, and research and development have been done on a lamp using LED (LED lamp). Recent market needs for saving energy and resource boost the demand for light bulb shaped lamps using LEDs (hereafter simply referred to as “light bulb shaped LED lamp” or “LED light bulb”) replacing conventional incandescent light bulbs using filament coils, and lighting apparatuses including the LED light bulbs.
Known properties of LEDs include reduced light output as temperature increases, which lead to shorter product life. In response to this problem, a metal case is provided between a semispherical globe and a base in a conventional LED light bulb so as to suppress the increase in the temperature of LED (for example, see Patent Literature 1).
The conventional light bulb shaped LED lamp disclosed in Patent Literature 1 shall be described as follows with reference to FIG. 52. FIG. 52 is a cross-sectional view of a light bulb shaped LED lamp according to the conventional art.
As illustrated in FIG. 52, the conventional LED lamp 1000 includes a translucent cover 1110 which is a semispherical globe, a base 1190 for receiving power, and an outer case 1200 which is a metal case.
The outer case 1200 includes a peripheral portion 1210 exposed to outside, a circular-plate light-source attachment 1220 integrally formed with the circumferential part 1210, and a recess 1230 formed inside of the circumferential portion 1210. On the upper surface of the light-source attachment 1220, an LED module 1130 which includes LEDs is mounted on a base platform. Note that, an insulator 1240 formed along the shape of the inner surface of the recess 1230 is provided on the inner surface of the recess 1230, and a lighting circuit 1180 for turning on the LEDs are housed in the insulator 1240.
With the conventional light bulb shaped LED lamp 1000 having the configuration described above, the outer case 1200 (metal case) in which the light-source attachment 1220 and the peripheral portion 1210 are integrally formed is used. The outer case 1200 functions as a heat sink for radiating heat generated at the LED to outside, and the heat generated at the LED is efficiently conducted from the light-source attachment 1220 to the peripheral portion 1210. With this, the increase in the temperature of the LED is suppressed, thereby preventing reduction of the light output from the LEDs.